Vehicle-mounted hoisting apparatus



L. L. EAKIN VEHICLE-MOUNTED HOISTING APPARATUS May 26, 1953 '5Sheets-Sheet 1 Filed May 6, 1947 May 26, 1953 I, L, EAKIN 2,639,825

YEHICLE-MOUNTED HOISTING APPARATUS Filed May 6. 1947 3 Sheets-Sheet 2Patented May 26, 1953 UN lTE-D S TATES PATENT F F 1 CE 2,639,825VEHICLE-MOUNTED HOIST iNG ArPARA'rU's Laurie L. Eakin,'Ventura, Calif;Application May 6, 1947, Serial No. 746,248

5 Claims.

My invention relates to hoisting apparatus, and particularly to atransporting vehicle, such as a motor truck, having means incorporatedthereon for hoisting relatively heavy objects and placing them. on andremoving them from the platform of the truck. The present invention isconcerned with a hoisting apparatus of the general type disclosed in mypending application for patent on Vehicle Hoist, Serial No. 712,652,filed November 2'7, 1946, now Patent No. 2,575,262. The priorapplication is directed to a novel form of hoisting boom for use onmotor trucks, while the present application embodies actuating means iorpivoting such a boom forwardly and rearwardly of the truck.

One object of my invention is to provide a mobile hoisting apparatuspreferably including a motor truck having a platform, a boom pivoted onan axis transversely of the truck platform adjacent the rearward endthereof to adapt it to pivot to an extended position. projectingrearwardly from the platform to receive a load which is attached to theend of a cable carried by the boom, and to a retracted position towardthe forward end of the vehicle to cause the object to be disposed overthe platform: so that it may be lowered onto the-platform. The inventionfurther provides a novel power-actuated means for pivotingv thehoistingboom to its different angular positions.

It is desirable in hoisting apparatus of this general type that thehoisting boom be adapted to": pivot through substantial-1y 180 degrees,that is, from a horizontal position extending forwardly fromits pivot toa horizontal position projecting rearwardly from the truck, so that theend of the boom may belowered to a point close to the ground. or to theobject which' is to be raised, It is preferable that hydraulicpowermeans be employed for pivoting the boom in order toobtain thepowernecessary to pivot the boom. when relatively heavy objects are beingliftedi In such apparatus, it isthe usual practice to operativelyconnect the piston of a hydraulic actuating' jack to a relatively shortarm projecting from the pivot of the boom in a downward direction. Sincethe'boom moves through substantially 180- degrees the arm likewiseswings through the same angle, and at the extreme forward andrearw'ardmovement of the arm the arm and piston approach alignment and this hasthe effect to cause a substantially dead center" condition. Due to thiscondition; a tremendous amount otpower' is required: to obtain the mechn cal adv ntage necessary to 2 overcome the weight of the boom and itssupported load. It is a further object of this invention to providemeans for augmenting the power produced by the usual hydraulic jack atthe start of the upward pivoted movementti'f the boom, so that adequatepower is provided for Overcoming inertia of the boom and initiating itsupward tilting movement. This object can best be accomplished by theprovision of airiliary or secondary fluid-actuating jacks, which areoperatiyeiy connected to the pivotal ild of the boom only when thelatter is at the orw rd and rearward extremities of its pivotalmovement, these jacks thus functior'iing to assist the main hydraulicjack in overcoming inertia ofthe lifting. boom; After the boom beentilted upwardly to a positionwhei-ein a greatly'improved mechanicaladvantage exists, sufficient power is derived from the main hydraulicjack to complete the pivotal movement of the team, and at this point theoperation of the auxiliary jacks is arrested. By prov ding a pair of theauxiliary fluid-actuated jacks and locatingone forwardly and onerearwardi of the piyotof the boom,- they may be selectively operated toassist in initially tilting the boom upwardly from both forward andrearward positions; and this is an important object of my invention.

It is another object of the I invention to provide means for cushioningthe load when lowering the boom, and, in this respect, i make use of theauxiliary fluid-actuated pistons which limit the downward tiltingmovement of the boom and which may be actuated in a manner to positivelycontrol the final downward swinging movement, to ease the boom slowlyand safiely' downwardly even when large loads are sustained thereby.

Another object is to provide, in a hoisting apparatus of the characterreferred to,- a hoist-- in'g boom of novel construction, capable ofsustaining great loads, and one which,- when in its forward inoperativeposition, will not interfere with objects located on the truck platformor other parts of the vehicle; Pref erably, the boom is of angular shapeso that its distal end is adapted to either overlie the cab oft-betruck, in close proximity thereto,- or'to be'dispose'dclosely adjacentthe rear side of the cab when the boom is in its" forward" inoperativeFurther objects of the invention are set forth in the followingspecification which describes several preferred embodiments thereof, byway of example, as illustrated by the accompanying drawings. In thedrawings:

Fig. 1 is a side elevational view of a motor truck equipped with oneform of hoisting apparatus, in accordance with my invention;

Fig. 2 is a plan view of the rearward end of the truck, with theplatform thereof removed to disclose the fluid-actuated means foroperating the hoisting boom;

Fig. 3 is a longitudinal sectional view, taken substantially on line 3-3of Fig. 2, and showing the relationship of the parts of the actuatingmeans when the boom is in its forward retracted position;

Fig. 4 is a view similar to Fig. 3, but illustrating the relationship ofthe parts when the boom is in its rearmost, extended position;

Fig. 5 is a rear View of the truck platform and the hoisting boom, inreduced scale, showing the boom in substantially upright position;

Fig. 6 is a view similar to Fig. 1, but illustrating a different form ofhoisting boom, and embodying a modified actuating means therefor;

Fig. '7 is a plan view of the modified actuating means;

Fig. 8 is a longitudinal sectional view, taken on line 8-8 of Fig. '7,showing the relationship of the parts of the actuating mechanism whenthe boom is in retracted position; and,

Fig. 9 is a view similar to Fig. 8, but showing the relationship of theparts when the boom is in rearmost position.

Referring first to Figs. 1 to 5 of the drawings, my improved hoistingapparatus is therein shown as installed on a conventional motor truckI0, which is provided with a platform II for supporting various objectsduring transportation, and a drivers cab I2 mounted on the chassis I3.Fixed to the side rails I4 of the chassis I3 are tubular bearings I5which are adapted to receive a tubular axle or pivot member I6 to adaptthe latter to rotate on an axis extending transversely of the truck,beneath its platform I I. Welded or otherwise secured to the ends of thetubular axle I6 are the ends of the arms I9 of a hoisting boom 20. Thearms I9 extend parallel to the lateral edges of the platform II. At asuitable distance forwardly of the axle l6 they are inclined upwardlyand inwardly (Figs. 1 and 5), and then extend substantially horizontallyso that their convergent ends meet. Through this construction the distalend of the boom is disposed above the cab I2 of the truck in relativelyclose relation thereto, to provide compactness and prevent the end fromprojecting upwardly to an extent where it might strike overhead wires,trees, and the like. In the present improved boom 20, the convergentarms I9 are joined by a cross-strut 2I which provides rigidity. At thepoint of joinder of the arms I9, a V-shaped element 22 is secured, thiselement being adapted to rotatably support a grooved pulley or sheath23. A cable 24 passes over the sheath 23 and has a hook 25 at one end.The other end of the cable 24 is wound around the drum 26 of a powerwinch, indicated at 21, such means not being herein shown in detail asthey may be of any suitable type generally employed in hoistingequipment.

The hoisting boom is adapted to be pivoted to any of the positionsindicated in Fig. 1 by means of fluid-actuated devices, to be nextdescribed.

The pivot tube or axle I6 has a pair of radial arms 38, which may bewelded thereto, each arm 30 being preferably made in two complementaryparts thereby providing a space therebetween for receiving the end of apiston rod 3I of a main hydraulic jack 32, the rods 3| being pivotallyconnected. to the arms 30 by pins 33. Each rod 3I carries a piston 34 atits forward end, the pistons being slidable in hydraulic cylinders 35which are pivotally connected to brackets 36 carried by a cross-member31 of the vehicle chassis I3. The ends of the cylinders 35 areconnected. by hydraulic lines 38 and 39 which lead to amanually-operable valve 40 (Fig. 2), which may be actuated toselectively introduce fluid under pressure into either end of thecylinders to actuate their pistons 34 which act through their rods 3|and the arms 30 to turn the pivot tube or axle I6 in either direction toswing the boom 20 between its two extents of movement illustrated byfull lines and dot-and-dash lines in Fig. 1. While the main hydraulicjacks 32 function to move the boom 20 through the major portion of itspivotal movement, the movement of the boom at the extreme forward andrearward ends of its movement is controlled by auxiliary fluid-actuatedmeans, to be presently described.

It will be observed by reference to Figs. 3 and 4 that when the boom isat the extent of its forward and rearward movement, the arms 30 extendnearly horizontal and an almost dead center relation exists between thearms 30 and the piston rods 3 I. Because of this very unfavorableleverage condition, and due to the fact that the great inertia caused bythe heavy boom and the weight supported thereby must be overcome, torqueof great magnitude mustbe applied to theaxle I6, and, since the momentarm 30 is relatively short, it is apparent that tremendous power isrequired to produce such force. For this reason it is very desirable,and quite essential, that the main hydraulic-actuating means be assistedduring the start of the pivotal movement of the boom upwardly from itsextended and retracted horizontal positions. In the pres ent inventionthis assisting means consists of auxiliary or secondary fluid-actuatedmeans to be next described.

Secured to cross-members 39 of the chassis l3, forwardly of the axle I6,is a hydraulic cylinder 44 in which a piston 45 is slidable. The piston45 has a rod 46 which extends rearwardly and has a cross-piece orfollower 41 at itsend. The upper portion of the follower 41 is adaptedto slide along a pair of guiding strips 48 extending longitudinally of,and attached to, the chassis I3. Secured to a cross-member '49 of thechassis, rearwardly of the pivot-tube or axle I6, is a second hydrauliccylinder 50 in which a piston 5| is slidable toward and away from theaxle. The rod 52 of the piston 5I has a follower 53, the upper portionof which is adapted to slide forwardly and rearwardly along a pair ofguiding strips 54. The auxiliary pistons 45 and 5| are slid in theirrespective cylinders by fluid introduced under pressure into theopposite ends of the cylinders through lines 55, 56, 51, and 58, theflow through the lines being controlled by a valve 60.

The followers 41 and 53, of the respective hydraulic piston rods 46 and52, are adapted to engage the opposite edges 65 and 66 of a wedgeshapedcam member 61 secured to and projecting radially from the pivot-tube I6.Assuming that the boom 20 is in its forward retracted position,

5. as shown by full lines l. and 3, the tollowers 41 and 53 will assumethe positions shown in the latter View what is to say, the follower 4is" disposed Close to the axis of the pivot-tube i6, and the" follower53 is located at a greater dis? tance'from the tube with the outer edge'66 of the cam member 6? resting thereagainst. The boom is thusmaintaihod at rest in its forward inorierativeposition with its cammember" 61 resting against the follower 53,.Whi'ohserves as a stop forlimiting the tilting movement of the boom in this direction.

'To' pivot the boom 20 to" the extended position, indioated by doti-andclash lines in Eigs. l and 4, to adapt it to lift a heavy object, suchas that shown at H1,- hydraulic fluid is introduced into the right-handends of the main hydraulicactuating cylinders 35 and theauxiliary:actual; ing cylinder 5 The main piston rods 3|, beingconnected to the aims Sliptend to rotate the pivot tube it? in clockwisedirection to thereby ioivot the boom 26 in the sameclirection. Dior--ing this initial pivotal movement, the iollo'wer 521 of the. piston'rod52 is forced forwardly; and, acting between the strips 54 and'theinclined: edge 6% of the cam member 61, forces the latterblownwar-diy,in the manner indicated by dot-and-d'ash lines in Fig. In. this manner,the auxiliary hydraulic means 50 augments the force applied by the mainhydraulic means 32 through the armsv 30 to the axle [6,- so that thetorque necessary to overcome inertia of the boom is readily attained.The movement of the follower 53 is relatively short, but is sufficientto swing the cam member 61, downwardly through an angle of approximately30 degrees, it having been determined that when the arms Ware moved tothis pQ-Sition the main hydraulic means 32 is able to complete thepivoting of the boom 28 without assistance. It is thus seen that theinitial pivotal movement of the boom is efifeoteo by the combined actionof the main and auxiliary hygiraulio means 32. and 50., while theremainder of the pivotal movement is produced by. the main m a s lon theboom zuappmeches the extent of: its earward ext nd ovement. the ed e. ofthe com member 61 strikes thefifollower- 41 of the piston rod 46 of theauxiliaryhydraulio means M in the manner shown by full lines in Fig. 4Thereafter the valve fill. is actuated to cause fluid be intr duced intothe right-hand end-of the cylinder 4.4; to etract the follower 41 alongthe he stri s, it. In this manner, the follower. it dforwardl along theinclined cam edge 65 to permit further pivotal movement of the boom inclockwise. direction. Thus, the boom M is nerrnitted to complete its.pivotal. movement to' the fully extended. position indioatedby dot-analdosh lines in Figs. 1 and 4.. During this movemerit, the main cylindersl'lfig ivot on the brackets. 35 The valves lil and; GB. may be. madeas aunit or coupled together in, any suitable manner, so that propersynchronization, of the actuation ofthe main and auxiliary hydraulicmeans. can be ef e t' i AfterthebQQm 8; has been extended, the. end.ofthe gable 25 may be connected to the object Hi, afteriwhich thesequence oi? operations is reversed to cause the boom to swing upwardlin counteroloektvise olireotion to lift, the object, and move it to anyposition, above the. truck platform. The power Winch, 21,15firstoperatecl to cause the cable 24; to lift, the objeot. 'lflroff thegr und; end the valvesll. aridfifl arethenactuated to effect as erationof? the hydrauliemeans. The-initial pivotal movement of me boom 21! iseflieoted. by'lthe simultaneoosaotuatiom or the main and secondaryhydraiulicmem s 3i and? '41. 'As the piston rod Ali is slid rearwardly,its iollov rer- 4 is romeo between the euiclin g'stri'os t8 and the camedge 65 so as to cause the 6am. member-'51 to be'rorced downwarlly; asshbwiibji full lines in Fig .4. The combined'toroes thus applied to thepivot tube l6 by theoietoils'm and 1'5 through the arms 39 and thernernlrrer '6 produces the torque hecessarv to overcome the combinedweight of the lifting boom 20 meow object" 10 supported thereby, andthus the boom is tilted upwardly in ouriterolbck'wise olirecti'on. Afterthee-am mem- 61' arrives at the position shown by full lines 4, theauxiliarir hydraulic means 44 has no further 'funetion and comes torest, the remainder of tile'pivotal movement of theboom'being effectedlay-the mainh vorauliome'ans 32; which may be actuated for a periodnecessary to' carry the objeet to Above the-location on: the'truckplatform where it is desired to support it during tra'iisporta-tion.boom 24!, being of a bifurceted construction, permits the object 10' tobe swung between its side members, as shown by dash lines in Fig; l, andit will beno'ted that'the cable t'll-passes across the coh'nectlnlgstrut 2! of the boono to nrevetit exoes'sive' swinging move: ment of theobject so that it can be deposited on the platform H with greateraccuracy. when the object i8 is disposed in the proper location,- thevalve M is manipulated to arrest the opera tion of the main. hydraulic"jacks 32; after which the cable 24 is pavedlou't fromihedium 26 to lmrer the object onto the platform. While the object. :9 hereinshownls onewhich may be set upon. the olatform' it willbeapparent that the boom 2ais capable or lifting and supporting other objects. such'as'poles, inuprightposition, to permil: them to'be erected in holesln the ground.The hoisting. apparatus "may thus be said tube universal in itsapialication to use,fiand ma be advantageously employed ontransportation and construction vehicle's; Moreover,' the hoistinequipment may bereadlly. applied coexisting trucks; with minimum changetheir structures.

The modified'oons'itruotion'of the hoisting apparatus: shown it; Figs/6- to9 is similar to that shown in the'prebedmg'viewsam the apparatusoperates to acoomplzsh the some results. In this alternative structure,a slightly different type of lifting boom 8o is shown as pivotallymounted on the truck 8L. 'The boom'lifl has opposite legs 82 which. whenthe boom'is in fully retracted positidn, extend along thsideof theplatform83 of thetmck, there'arward ends of: the legs being connected'totheencl's oi a transversely extending nivotvtube or.axle' 84.' Ataxpoint adjacent the rear of the; deb Biof the truck,'the legs 82project upward-Imus shown ati 8 6. ,"and above. the top of hefcab, t eyxt ndxinw rdiy'to provide hori: zrq te e nnec ine-m t os; n; e-- Bet eendio ni-es'ns e fire r o sth a c ble eers .8 i e e x -el c ed e b e 89: wi'ng' 'therarouncihavirie a Book 90 at'its end; The cab e i!- i enneeieo. a. ow n 9!, fl b" 1i tor t invention. 2 edert d opivqt shown b ull lies. .ie iiiee fi e d et-ee deh i es nfl e 6 ,enqr eeve se-l A elio 's trli p e e leey o the e entporooos. i or he e e we who. position; thecablefl'passe's across this strut, and

the b m is in tsextenoed,

thus interference of the cable with the truck platform or objectsthereon is avoided.

As in the first construction, the boom 80 is pivoted throghout the majorportion of its movement by main hydraulic means I00, while its initialmovement is effected by the combined actuation of the means I andauxiliary hydraulic means IOI and I02. The main hydraulic means includesa pair of pivoted cylinders I03 in which pistons I04 are adapted toslide, the pistons having rods I05 pivotally connected to arms I06projecting radially from the pivot-tube or axle 84. The auxiliaryhydraulic means I0! and I02 consist of cylinders I09 and H0,respectively, which are affixed to cross-members I I I of the truckchassis. Pistons I I3 and IM slidable in the cylinders I09 and II 0 haverods H5 and HG, the lower ends of which are adapted to engage ears II!and H8 projecting laterally in opposite directions (Fig. 7) from an armI I9 fast on the axle 84.

When the boom 80 is in forward retracted position, the piston rod H6 isretracted in the cylinder H0, and the arm H9 is disposed in thesubstantially horizontal, rearwardly extending position, shown in Figs.7 and 8, with the ear II8 engaged with the lower end of the piston rod.To pivot the boom 80 toward a rearward extended position hydraulic fluidis introduced simultaneously into the right-hand end of the maincylinder I03 and the upper part of the auxiliary cylinder I I0. Thepiston rods I05, acting through the arms I 05, tend to rotate the axle84 in clockwise direction, and this operation is augmented by the pistonrod I I! which, through its engagement with the ear IIB of the arm II9,forces the latter downwardly, as indicated by dot-and-dash lines in Fig.9. When the piston rod H6 completes its movement in this direction, thepiston rod I05 operates alone to complete the pivotal movement of theboom. As the boom 80 and arm I I9 arrive at the position indicated bydash lines in Fig. 8, the ear I I? of the arm I I 9 engages the end ofthe auxiliary piston rod I I 5 to cushion the descent of the boom. Thepiston rod H5 is then retracted into the cylinder I09, as shown in Fig.9, to permit further pivotal movement of the boom to fully extendedposition.

After the cable 09 is connected to an object I20, as shown in Fig. 6,hydraulic fluid is introduced into the left-hand ends of the maincylinders I03 and into the upper end of the auxiliary cylinder I09. Theiston rod I I5 thus forces the arm 'I I9 downwardly, to the positionshown by dash lines in Fig. 8, after which the main piston rods I05complete the tilting movement of the boom toward its forward retractedposition. When the object I20 is positioned over the area of theplatform 83, where it is to be deposited, the actuation of the mainhydraulic means I00 is arrested and the object lowered by paying out thecable 89 from the drum 9|. The introduction of hydraulic fluid into theopposite ends of the cylinders I03, I09, and H0, may be controlled by asuitable valve or valves, not herein shown.

While I have herein shown and described the improved hoisting apparatus,as embodied in two preferred forms of construction and applied. tov

use with a particular type of vehicle, by way of example, it will beapparent that the construction of the apparatus and its application to.use may be varied in certain respects without departing from the spiritor scope of the invention.

8 Therefore, without limiting myself in this respect, I claim:

1.- In a vehicle, hoisting means for loadin ob- ,iects on and unloadingthem from the vehicle, including: a boom pivoted transversely of thevehicle to adapt it to pivot to a forward position overlying thevehicle, to a rearward position projecting rearwardly from the vehicle,and to positions intermediate said forward and rearward positions, saidboom having an arm and a stop element projecting radially from itspivotal end; primary fluid actuated means connected to said arm andoperable to pivot said boom through the major portion of its movement ineither direction; a air of secondary fluid actuated pistons disposedforwardly and rearwardly respectively of the pivotal point of the boomand adapted to be moved to extended position to engage said stop elementto limit the pivotal movement of said boom, and adapted to be moved toretracted position to permit said boom to complete its pivotal movementto extreme forward and rearward positions under the influence ofgravity, said pistons being also operative, upon movement to extendedposition, to initially pivot said boom in a direction away from itsforward and rearward positions.

2. In a vehicle, hoisting means for loading objects on and unloadingthem from the vehicle, including: a boom pivoted transversely of thevehicle to adapt it to pivot to a forward position overlying thevehicle, to a rearward position projecting rearwardly from the vehicle,and to positions intermediate said forward and rearward positions, saidboom having an arm and a stop element projecting radially from itspivotal end; primary fluid actuated piston means connected to said armand operable to pivot said boom through the major portion of itsmovement in either direction; a pair of secondary fluid actuated pistonsdisposed forwardly and rearwardly respectively of the pivotal point ofthe boom and adapted to be moved to extended position to engage saidstop element to limit the pivotal movement of said boom, and adapted tobe moved to retracted position to permit said boom to complete itspivotal movement to extreme forward and rearward positions under theinfluence of gravity, said pistons being also operative, upon movementto extended position, to tilt said stop element to initially pivot saidboom in a direction away from its forward and rearward positions. 3. Ina vehicle, hoisting means for loading objects on and unloading them fromthe vehicle, including: a boom pivoted transversely of the vehicle toadapt it to pivot to a forward position overlying the vehicle, to arearward position proectmg rearwardly from the vehicle, and to positionsintermediate said forward and rearward positions, said boom having anarm and a cam projecting from its pivotal end; primary fluid actuatedpiston means connected to said arm and operable to pivot said boomthrough the major portion of its movement in either direction; a pair ofsecondary fluid actuated pistons disposed forwardly and rearwardlyrespectively of the pivotal pointof the boom, and adapted to be moved toextended position to engage said cam to limit the pivotal movement ofsaid boom, and adapted to be moved to retracted position to permit saidboom to complete its pivotal movement to extreme forward and rearwardpositions under the influence of gravity, said secondary pistons beingalso operative, upon movement to extended position and relative to saidcam, to initially pivot said boom in a direction away from its forwardand rearward positions.

4. A vehicle hoist comprising a frame, a boom pivoted on said frame formovement from a position extending in one direction from the axis of thepivot to an intermediate raised position and to a position extending inthe other direction, an arm extending from the pivotal end of the boom,a primary fluid actuated cylinder and piston operatively connected tosaid frame and said arm for movingsaid boom from one position toanother, a cam arm extending from said pivotal end of said boom, 2.first auxiliary fluid cylinder and piston operative between said frameand said cam arm for initially moving said boom from its said positionextending in one direction for assisting' said primary cylinder andpiston, and a second auxiliary fluid cylinder and piston operativebetween said frame and said cam arm for assisting said primary cylinderand piston for initially moving said boom from its position extending inthe said other direction.

5. A vehicle hoist comprising a frame, a boom pivoted to said frame formovement from an extreme position extending in one direction from theaxis of the pivot to an intermediate position and to an extreme positionextending in the other direction from said pivot, an arm extending fromthe pivotal end of the boom, a primary fluid actuated cylinder andpiston operatively connected 30 Number to said frame and said arm formoving said boom from one position to another, a cam arm extend- 10 ingfrom said pivotal end of said boom, auxiliary cylinder and piston meansmounted on said frame, cam follower means connected to said auxiliarycylinder and piston means and engageable with said cam arm and with saidframe, said cam arm having a cam surface contour whereby the principalmechanical advantage is obtained when said boom is at either of itsextreme positions whereby said auxiliary cylinder and piston meansassists said primary cylinder and piston for initially causing themovement of said boom from said extreme positions.

LOURIE L. EAKIN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,019,268 Melzer Mar. 5, 1912 1,817,859 Cohen-Venezian Aug. 4,1931 2,181,253 Willis Nov. 28, 1939 2,220,815 Feilcke Nov. 5, 19402,244,559 Lawton June 3, 1941 2,290,738 Chadwick July 21, 1942 2,353,655Day July 18, 1944 2,360,654 Day Oct. 1'7, 1944 2,426,829 Le TourneauSept. 2, 1947 2,433,598 Chadwick Dec. 30, 1947 FOREIGN PATENTS CountryDate 318,330 Great Britain Sept. 5, 1929

